The conventional ocean has potential hydrokinetic energy because the current of the ocean has stable speed and direction. For example, the Kuroshio current flows toward north consistently and the speed is about 1 m/s at the distance about 1 km from Taiwan, and the width is about 150 km. If a two-blade turbine ocean current generator of 1 MW is set offshore from the island of Lyudao about 3 kin, there is an area about 25 square km where the Kuroshio current has the highest current speed. The two-blade turbine ocean current generator is estimated to generate energy of 1 GW to 3 GW, and which is equal to the designated amount of power of three nuclear power plants. Furthermore, ocean current generator is more environmentally-friendly when compared with the existed power plants using nuclear power. Therefore, the use of ocean current is intensively studied and becomes the main stream of study for getting energy from the natural sources.
FIG. 1 shows the conventional water turbine and comprises two sets of generators 10 and each of which has at least one blade 101, two lifting wings 20 are connected between the two sets of generator 10. A cable 30 is connected between the generators 10 and the sea bed 40. The blades 101 rotate by the current to generate electric power. The current passes the lifting wings 20 to keep the generators 10 to be lifted and maintained at the effective area. The cable 30 ensures that the generators 10 are positioned within the effective area. However, the cable 30 can only position the generators 10 in shallow area, when the depth of the ocean is over 200 meters, the sea bed 40 is thousands of meters from the water surface. Therefore, the conventional generators can only be set close to the land and the current speed is too slow to effectively drive the generators 10. The depth of the ocean at the east coast of Taiwan is about 1000 to 4000 meters, and it is difficult to fix the cable 30 on the sea bad 40. The maintenance will be difficult when the climate conditions become bad. Typhoons can easily damage the generators 10 and the blades 101 are difficult to face the currents because the currents have different directions so that the efficiency of the generators 10 is low. The lifting force of the lifting wing 20 is affected by the density of the water and the speed, and the density and speed change along with time, so that the generators 10 may not be located at desired positions.
FIG. 2 discloses a conventional turbine generator 50 with multiple blades 501. A power retrieving station 60 floats on the surface and has a positioning cable 601 which is connected to the turbine generator 50. A buoyant 70 is connected in parallel to the power retrieving station 60 by a fixing cable 701. The buoyant 70 has an indexing device 702 which is connected in parallel to the turbine generator 50 by a cable 703. A cable 80 is connected between the indexing device 702 and the sea bed 90. The power retrieving station 60 and the buoyant 70 float on the water surface to maintain the turbine generator 50 so that the turbine generator 50 is located in the effective area where the current is usable. The sea bad 90 at the deep ocean makes the installation and maintenance be a huge task. The bad climate can easily damage the turbine generator 50 and the change of the current affects the efficiency of the turbine generator.
The present invention intends to provide a self-positioning device for water generators and improves the shortcomings of the conventional ones.